Research On Optimization Of Relay Selection In Cooperative Communication

Wireless communication has been rapidly developed and widely used in recent years,but its existence of multiple fading has seriously affected the further development.The Multiple-Input Multiple-Out?MIMO?technology provides a way to improve the performance degradation caused by multiple fading,but the application of MIMO technology is limited by the need to install Multiple antennas on mobile terminals.Therefore cooperative communication technology is proposed.In a cooperative network system,the channel status of the selected relay node is an important factor affecting network performance,so the selection of the relay is particularly important to the cooperative network.At present the research on cooperative relay mainly concentrated in selected multiple potential relay which what collaboration,relay or under what conditions to collaborate and what collaboration strategy.In order to improve the performance of the system and select the effective relay,this paper carried on a further study on the basis of the research and development of the current relay selection.The main contents and innovation points of this paper are as follows:This paper first analyzes the threshold strategy based amplify-and-forward?AF?relay selection algorithm.On the basis of guarantee the bandwidth efficiency,in order to reduce the system symbol error rate?SER?,improve the reliability of system,combined with hybrid decoder-amplify-forward thought,increase in the existing threshold algorithm decode-and-forward?DF?relay cooperation agreement,puts forward the improved hybrid protocol relay selection algorithm based on threshold.Based on the original algorithm,this algorithm only increases the comparison of the signal to noise ratio?SNR?in one step,and the implementation is relatively simple.Through analysis and simulation show that this scheme can without changing the original bandwidth efficiency on the basis of effectively reduce the SER,when the potential of relay nodes is 4,the selection of threshold beta is 0.01,SER is 10^-5,SNR compared to the adoption of the strategy of AF relay selection algorithm by about 0.7 dB.When the input SNR in the system becomes larger,the performance improvement of the SER is more obvious,and the reliability of the system is further improved.In the above study,the relay node works in the half-duplex state,considering that the time division duplex transmission needs at least two time slots and the interference between the signals can be neglected.In the full-duplex relay cooperative system,the relay can transmit information in one time slot by installing two antennas to increase the transmission rate.However,due to the distance problem between the two antennas,the relay receives its own transmission signal while receiving the source signal and then generates self-ring interference.For the system to achieve better interrupt performance,combined with full duplex and half duplex advantages,resulting in a hybrid duplex system.This paper choose a relay based on an existing cooperative system with two duplex modes.The scheme selects one of the optimal relays and works together from two modes of work.Through theoretical analysis and software simulation,it shows that this scheme compared to the model under the optimal relay selection algorithm based on the first jump,greatly reduce the number of interrupt system,improve the performance of interruption.With the change of input SNR,potential relay number and minimum requirement transmission rate,this paper can provide better performance of interruption,thus effectively improving the stability of the system.